How long does the average 1" residential value under proper design and duty, last before it's diaphram needs to be replaced?

I've got a yard full of Rain Bird PEB valves at home that are around 12 years old now (about 96 of them). Never had to tear a single one down yet or repair one. My mom's house has some Rain Bird brass valves that were installed in 1986. Of the 12 valves in that yard at least 8 of them are original and have never been cracked open or re-built. I think it all depends on how the system is designed, what the water is like and what kind of pressure you have. Of course if you install junk to begin with then it won't last very long.

It really depends on the valve you're talking about. The Hunter SRV seems to only last about 5 - 10 years, others last longer and some less. I've found that the valves without any plastic in the diaphragm are more durable than those with it. The plastic parts (like the ring on the bottom of the SRV diaphragm) are always the first to go.